We present the construction of a continuous, daily (09:00 UTC), station‐based (Azores–Iceland) North Atlantic Oscillation (NAO) Index back to 1871 which is extended back to 1850 with additional daily mean data. The constructed index more than doubles the length of previously existing, widely available, daily NAO time series. The index is created using entirely observational sea‐level pressure (SLP) data from Iceland and 73.5% of observational SLP data from the Azores – the remainder being filled in via reanalysis (Twentieth Century Reanalysis Project and European Mean Sea Level Pressure) SLP data. Icelandic data are taken from the Southwest Iceland pressure series. We construct and document a new Ponta Delgada SLP time series based on recently digitized and newly available data that extend back to 1872. The Ponta Delgada time series is created by splicing together several fractured records (from Ponta Delgada, Lajes, and Santa Maria) and filling in the major gaps (pre‐1872, 1888–1905, and 1940–1941) and occasional days (145) with reanalysis data. Further homogeneity corrections are applied to the Azores record, and the daily (09:00 UTC) NAO index is then calculated. The resulting index, with its extended temporal length and daily resolution, is the first reconstruction of daily NAO back into the 19th Century and therefore is useful for researchers across multiple disciplines.

中文翻译：

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每日亚速尔群岛-冰岛北大西洋涛动指数回溯至 1850 年。


我们提出了一个连续的每日（09:00 UTC）基于站点（亚速尔群岛 - 冰岛）北大西洋涛动 (NAO) 指数的构建，该指数可追溯到 1871 年，该指数可追溯到 1850 年，并带有额外的每日平均数据。构建的指数是先前存在的、广泛使用的每日 NAO 时间序列长度的两倍多。该指数完全使用冰岛的观测海平面压力 (SLP) 数据和亚速尔群岛 73.5% 的观测海平面压力 (SLP) 数据创建，其余部分通过再分析（二十世纪再分析项目和欧洲平均海平面压力）SLP 数据填写。冰岛数据取自冰岛西南部压力系列。我们根据可追溯到 1872 年的最近数字化和新可用数据构建并记录了一个新的蓬塔德尔加达 SLP 时间序列。蓬塔德尔加达时间序列是通过将多个断裂记录（来自蓬塔德尔加达、拉日什和圣玛丽亚）拼接在一起创建的，用再分析数据填补了主要空白（1872年之前、1888-1905年和1940-1941年）和偶尔的空白（145天）。对亚速尔群岛记录进行进一步的同质性修正，然后计算每日（09:00 UTC）NAO 指数。由此产生的索引具有扩展的时间长度和每日分辨率，是 19 世纪每日 NAO 的首次重建，因此对跨学科的研究人员非常有用。